Micro-budget Aussie chiller “The Tunnel” has taken the multi-platform release strategy to a new level.

The film was released for free on peer-to-peer sites that sometimes host pirated pics, in theaters, on a 2-disc DVD set and on iTunes and other digital platforms.

But despite the free viewings, producers say the pic, which cost about $135,000, will be in profits by the end of the year.

Filmmakers rounded up 50,057 $1 donations for a frame of film to kickstart production, and initial footage helped secure feevee and DVD distrib deals.

Co-producers Julian Harvey and Enzo Tedeschi launched “Tunnel,” directed by Filipino Carlo Ledesma, May 18, 2011, eventually totalling 4 million legal downloads on peer to peer networks. It has sold sold 25,000 units at up to $30 each on DVD, with an upcoming anniversary collector’s edition on Blu-Ray.

Co-written by Harvey and Tedeschi, “The Tunnel” is a docu-style story set in Sydney’s abandoned underground railway tunnels, where a film team try to find out why the government has scrapped plans to tap a reservoir of water that has become trapped there.

“Heavy peer-to-peer users happened to overlap really nicely with the core demographic for the film we were trying to make,” said Harvey. “You have more success with a genre film because they have a large, passionate following. I’m not sure you could fund your next romantic comedy this way but sci-fi, horror and genre films can work.”

Tedeschi says the innovative business model was not just about revenue. “It depends on what your goals are, it was a good way to get our first film up, a great way to get noticed and a way to maintain a lot of creative freedom,” Tedeschi added.

The pair also found that online streaming provided a surprising source of revenue, which is still being tallied.

Paid streaming from other Oz sites offered revenue sharing and licensing fees, though filmmakers say they didn’t always maximize the digital opportunities.

“For example, we generated millions of hits on our content on YouTube but we did not set up an ad share revenue until very late in the process.

“We found that when you add up a number of these non-traditional streams you can not only reach a huge audience but they can also start to create a decent and ongoing return to a filmmaker.”

Encouraged by their unlikely success, Harvey and Tedeschi are already working on a sequel, “The Tunnel: Dead End,” which has development funding provided the more traditional way — by Screen Australia. It will be a bigger-budget affair at $1 million.